CN110877045B

CN110877045B - Soil microorganism electrochemical restoration device, restoration method and application

Info

Publication number: CN110877045B
Application number: CN201911154414.9A
Authority: CN
Inventors: 李晓晶; 张晓林; 李月; 陈晓东; 李永涛
Original assignee: Agro Environmental Protection Institute Ministry of Agriculture
Current assignee: Agro Environmental Protection Institute Ministry of Agriculture
Priority date: 2019-11-22
Filing date: 2019-11-22
Publication date: 2021-06-25
Anticipated expiration: 2039-11-22
Also published as: CN110877045A

Abstract

The invention relates to the technical field of soil remediation, in particular to a tubular activated carbon air cathode, a soil microbial electrochemical remediation device, a remediation method and application. The tubular active carbon air cathode provided by the invention comprises a porous PVC tube (4) and an active carbon air cathode sheet (3) wrapped on the outer surface of the porous PVC tube (4); a cathode lead (5) is inserted between the porous PVC pipe (4) and the active carbon air cathode sheet (3), and the cathode lead (5) is exposed; the active carbon air cathode sheet (3) comprises an active carbon catalysis layer, a stainless steel net and a diffusion layer which are sequentially laminated; the diffusion layer is in contact with the porous PVC pipe (4). According to the invention, the active carbon air cathode sheet is wrapped on the outer surface of the porous PVC pipe, so that the cathode is ensured to be convenient to use, the efficiency of repairing polluted soil and desalting soil by the cathode can be improved, and the electrogenesis performance of an electrochemical system is improved.

Description

Soil microorganism electrochemical restoration device, restoration method and application

Technical Field

The invention relates to the technical field of soil remediation, in particular to a tubular activated carbon air cathode, a soil microbial electrochemical remediation device, a remediation method and application.

Background

China is a large country for petroleum production and consumption, over 400 exploratory and developed oil and gas fields and reservoirs are distributed in 25 provinces, cities and autonomous regions, the relevant operation range is about 20 ten thousand square kilometers, the ground crude oil of each well has a spread radius of 20-40 meters, and as about 700 thousand tons of petroleum fall each year due to exploration and exploitation work, and leakage accidents in the process of conveying and storing, the soil of a certain area is polluted by petroleum in different degrees. At present, the main petroleum polluted soil remediation technologies comprise physical remediation, chemical remediation and biological remediation.

The physical repair mainly comprises direct burning, leaching separation, thermal desorption, stable solidification, electric repair and the like. Wherein, the direct incineration is effective for the petroleum polluted oil sludge with high concentration, and the applicability to the petroleum soil with medium and low concentration is lower. Leaching separation and thermal desorption can remove part of petroleum hydrocarbon substances in soil, but pollutant elimination is not thorough. The solidification and stabilization method is adopted to treat the petroleum polluted soil, obviously harmful substances are not eradicated, and the potential activation danger exists. The electric restoration needs good mass transfer to achieve the expected effect, and the inherent mass transfer difficulty of the soil limits the exertion of the efficiency of the method to a certain extent. Physical remediation of contaminated soil plays an important role in early soil remediation, but the disadvantages of high input cost, low environmental safety and the like are not in accordance with the shortage of resources and sustainable development of ecological environment.

The chemical restoration mainly comprises chemical reagent extraction, oxidant oxidation, photocatalytic oxidation and the like. The chemical reagent extraction method is relatively effective for centralized high-concentration petroleum-polluted soil or oil sludge, and has low applicability to treatment of large-area and low-concentration petroleum-polluted soil. Oxidizer oxidation, which is a process of injecting a strongly oxidizing chemical agent into contaminated soil, is a process of removing petroleum pollutants while generating a large amount of toxic and harmful (gaseous) substances, and thus has a high environmental risk. The photocatalytic oxidation method requires light irradiation as the name suggests, but the light transmittance of the petroleum-polluted soil is poor, which hinders the practical application of the technology. Similar to physical remediation, chemical remediation has a certain effect in the remediation of petroleum-contaminated soil, but has the defects of great destructiveness on the original habitat of the soil, inevitable high environmental risk, high cost and the like, and is not beneficial to the long-term and large-scale implementation of the technology.

Bioremediation includes microbial and phytoremediation. Microbial remediation includes two modes of bio-addition and bio-stimulation. The biological addition refers to a method for biologically degrading and removing pollutants by adding screened high-efficiency degrading microorganisms into polluted soil, the general petroleum-polluted soil is relatively barren, and the reaction activity of the added microorganisms is inhibited due to the fact that the highly toxic substances such as polycyclic aromatic hydrocarbon and the like are contained. Therefore, when the bio-addition method is adopted to repair the petroleum-polluted soil, the bio-stimulation method is often accompanied by the addition and strengthening of nutrient substances such as nitrogen, phosphorus and the like. Nevertheless, the repair by microorganisms still requires a long repair period, and the removal effect of macromolecular, highly toxic and difficult-to-degrade petroleum hydrocarbon substances is relatively poor. Plant restoration, as its name implies, is a method of removing contaminants by planting plants and utilizing the action of the plant's root system. This method is obviously limited by climate and season, and in addition to long repair cycles, the costs of post-maintenance and plant body disposal are high. Similar to microbial remediation, phytoremediation has high environmental safety, but has poor removal effect on macromolecular, highly toxic and difficult-to-degrade petroleum hydrocarbon substances.

The existing physical, chemical and biological repair technologies are all pure energy input type treatment methods, and the obtained effect is only to remove pollutants, particularly, physicochemical measures are not excessive to improve the original quality and habitat of soil, and are not related to resource recovery. Many oil and gas fields in China are located in coastal areas, the soil is seriously salinized, particularly yellow river delta, Liaoling estuary, Yangtze estuary and the like, such as Daqing oil fields, Shengli oil fields, Central China oil fields, Hongkong oil fields and the like, and large areas of petroleum-polluted saline-alkali soil are generated. For the extremely deteriorated polluted soil, the development of a method for synchronously improving the soil by soil remediation and energy recovery is of great significance.

Disclosure of Invention

The tubular activated carbon air cathode has high electrochemical performance, and the soil microbial electrochemical restoration device assembled by the tubular activated carbon air cathode and the carbon rod anode can restore petroleum-polluted soil and simultaneously generate electricity and desalt, so that the tubular activated carbon air cathode has an industrial progress.

In order to achieve the above object, the present invention provides the following technical solutions:

the invention provides a tubular active carbon air cathode, which comprises a porous PVC tube 4 and an active carbon air cathode sheet 3 wrapped on the outer surface of the porous PVC tube 4; a cathode lead 5 is inserted between the porous PVC pipe 4 and the active carbon air cathode sheet 3, and the cathode lead 5 is exposed; the active carbon air cathode plate 3 comprises an active carbon catalysis layer, a stainless steel mesh and a diffusion layer which are sequentially laminated; the diffusion layer is in contact with the porous PVC pipe 4.

Preferably, the diameter of the holes on the porous PVC pipe 4 is 0.1-1 cm, and the distance between the holes is 0.5-2 cm.

Preferably, the thickness of the activated carbon air cathode sheet 3 is 1-4 mm.

Preferably, the cathode lead 5 is a titanium sheet; one end of the cathode lead 5 is flush with the bottom surface of the porous PVC pipe 4, and the other end of the cathode lead is higher than the top surface of the porous PVC pipe 4.

The invention also provides a soil microorganism electrochemical restoration device, which comprises a box body, a box cover, the tubular active carbon air cathode and a carbon rod anode, wherein the tubular active carbon air cathode is arranged in the box body;

the upper end of the box body is provided with an opening, an openable box cover is arranged above the box body, the box cover is provided with a first through hole, the bottom of the box body is provided with a second through hole opposite to the first through hole, and the tubular active carbon air cathode penetrates through the box cover and the box body through the first through hole and the second through hole;

the carbon rod anode is arranged between the tubular active carbon air cathode and the side wall of the box body; the carbon rod anode comprises a carbon rod 1 and an anode lead 2 connected with the carbon rod 1;

the box cover is provided with a first through hole and a second through hole, the first through hole is used for leading out an anode lead 2 of the carbon rod anode, and the second through hole is used for supplementing soil and moisture.

Preferably, four carbon rods 1 are uniformly distributed on the periphery of the tubular active carbon air cathode; the four carbon rods are connected through an anode lead 2.

Preferably, the box cover is connected with the box body through a flange.

The invention also provides a soil microorganism electrochemical remediation method, which comprises the following steps:

mixing tested soil, carbon fiber and water to obtain slurry;

placing the slurry in a box body of the soil microorganism electrochemical restoration device in the technical scheme, and adding water into the slurry through the second through hole for liquid sealing;

and connecting the anode lead 2 of the carbon rod anode with the cathode lead 5 of the tubular active carbon air cathode through an external resistor to carry out microbial electrochemical repair.

Preferably, during the preparation of the slurry, the dosage ratio of the tested soil, the carbon fiber and the water is 3300 g: 1.65-13.2 g: 0.7-2L.

The invention provides the application of the soil microorganism electrochemical remediation device or the method in the technical scheme in the synchronous power generation and desalination for remediation of petroleum-polluted soil.

The invention provides a tubular active carbon air cathode, which comprises a porous PVC tube 4 and an active carbon air cathode sheet 3 wrapped on the outer surface of the porous PVC tube 4; a cathode lead 5 is inserted between the porous PVC pipe 4 and the active carbon air cathode sheet 3, and the cathode lead 5 is exposed; the active carbon air cathode plate 3 comprises an active carbon catalysis layer, a stainless steel mesh and a diffusion layer which are sequentially laminated; the diffusion layer is in contact with the porous PVC pipe 4. In the invention, the porous PVC pipe is used for supporting the cathode and exposing the cathode to air to realize cathode reduction reaction, and the porous PVC pipe is used as a framework, and the active carbon air cathode sheet is wrapped on the outer surface of the porous PVC pipe, so that the efficiency of repairing polluted soil by the cathode and desalting the soil can be improved, and the electrogenesis performance of an electrochemical system can be improved; in addition, the preparation process of the tubular activated carbon air cathode provided by the invention is simple and convenient, and can be repeatedly reused.

The invention also provides a soil microorganism electrochemical restoration device, which comprises a box body, a box cover, the tubular active carbon air cathode and a carbon rod anode, wherein the tubular active carbon air cathode is arranged in the box body; the upper end of the box body is provided with an opening, an openable box cover is arranged above the box body, the box cover is provided with a first through hole, the bottom of the box body is provided with a second through hole opposite to the first through hole, and the tubular active carbon air cathode penetrates through the box cover and the box body through the first through hole and the second through hole; the carbon rod anode is arranged between the tubular active carbon air cathode and the side wall of the box body; the carbon rod anode comprises a carbon rod 1 and an anode lead 2 connected with the carbon rod 1; the box cover is provided with a first through hole and a second through hole, the first through hole is used for leading out an anode lead 2 of the carbon rod anode, and the second through hole is used for supplementing soil and moisture. The soil microorganism electrochemical remediation device provided by the invention can degrade soil pollutants by using indigenous microorganisms in soil; the device provided by the invention is reasonable in design, and the box body, the tubular active carbon air cathode and the carbon rod anode can be repeatedly utilized for multiple times, so that the device is more practical in industrial application.

Drawings

FIG. 1 is a diagram of a soil microbial electrochemical remediation device according to an embodiment of the present invention; the system comprises a carbon rod 1, a titanium wire 2, an active carbon air cathode sheet 3, a porous PVC tube 4, a titanium sheet 5, an external resistor 6 and a multichannel voltage signal acquisition system 7, wherein the carbon rod is connected with the external resistor 6;

FIG. 2 is a graph showing the voltage output and the ambient temperature during the electrochemical remediation process of soil microorganisms according to the present invention, wherein darker colors are the output voltage and lighter colors are the temperature.

FIG. 3 is the accumulated electric quantity during the electrochemical remediation process of soil microorganisms;

FIG. 4 is a soil sampling position after electrochemical remediation of soil microorganisms; wherein S1 is the region between the cathode and the anode near the cathode, S2 is the region between the anode and the side wall of the tank near the anode, S3 is the region between the anode and the side wall of the tank near the side wall of the tank; s4 is the cathode vicinity, S5 is the two anode middle regions, S6 is the box side wall vicinity;

FIG. 5 is a graph of the total petroleum hydrocarbon removal from soil after electrochemical remediation by soil microorganisms; wherein CK is contrast treatment, S1-S6 are different sampling points, and different lower case letters represent significant difference among groups;

FIG. 6 shows the removal of alkanes from soil after electrochemical remediation by soil microorganisms; wherein CK is contrast treatment, S1-S6 are different sampling points, and different lower case letters represent significant difference among groups;

FIG. 7 shows the removal of aromatic hydrocarbons from soil after electrochemical remediation by soil microorganisms; wherein CK is contrast treatment, S1-S6 are different sampling points, and different lower case letters represent significant difference among groups;

FIG. 8 shows the removal of polar materials and asphaltenes from soil after microbial electrochemical remediation; wherein CK is contrast treatment, S1-S6 are different sampling points, and different lower case letters represent significant difference among groups;

FIG. 9 shows the salinity content of the soil after the electrochemical remediation by soil microorganisms; wherein OS is original soil, CK is contrast treatment, S1-S6 are different sampling points, and different lower case letters represent significant difference among groups;

FIG. 10 shows the change in conductivity of soil after electrochemical remediation by soil microorganisms; wherein OS is original soil, CK is contrast treatment, S1-S6 are different sampling points, and different lower case letters represent significant difference among groups;

FIG. 11 shows the salt recovery in the tubular activated carbon air cathode of the soil microbial electrochemical system;

FIG. 12 shows the pH change of soil after electrochemical remediation by soil microorganisms; where OS is the original soil, CK is the control treatment, S1-S6 are different sample points, and different lower case letters indicate significant differences between groups.

Detailed Description

The tubular active carbon air cathode provided by the invention comprises a porous PVC tube 4, wherein the hole of the porous PVC tube 4 is preferably a round hole, and the diameter of the round hole is preferably 0.1-1 cm, and more preferably 0.5 cm; the circular holes are arranged in an array; the hole pitch is preferably 0.5 to 2cm, and more preferably 1 cm. In the invention, the outer diameter of the porous PVC pipe 4 is preferably 2-8 cm, and more preferably 5 cm; the inner diameter is preferably 1.5-7.5 cm, and more preferably 4.5 cm; the length is preferably 5-20 cm, and more preferably 15 cm.

The tubular active carbon air cathode provided by the invention comprises an active carbon air cathode sheet 3 wrapped on the outer surface of the porous PVC tube 4, wherein the active carbon air cathode sheet 3 comprises an active carbon catalysis layer, a stainless steel mesh and a diffusion layer which are sequentially laminated; the diffusion layer is in contact with the porous PVC pipe 4.

In the invention, the thickness of the diffusion layer is preferably 0.5-2 mm, and more preferably 1 mm; the diffusion layer is preferably a conductive carbon black diffusion layer. In the invention, the thickness of the stainless steel net is preferably 0.1-0.5 mm, and more preferably 0.3 mm; the mesh size of the stainless steel mesh is preferably 20-80 meshes, and more preferably 60 meshes. In the invention, the thickness of the activated carbon catalyst layer is preferably 0.5-2 mm, and more preferably 1 mm; the loading capacity of the activated carbon catalyst layer on the stainless steel mesh is preferably 0.1-0.3 g-cm^-2More preferably 0.19 g.cm^-2. In the invention, the activated carbon catalyst layer is a hydrophilic layer, the thickness of the activated carbon catalyst layer is limited to 1mm, on one hand, the activated carbon catalyst layer can better adsorb moisture to promote salting out, and on the other hand, the activated carbon catalyst layer can also play a role in protecting an electrode.

In the present invention, the method for preparing the activated carbon air cathode sheet preferably comprises the steps of:

placing the stainless steel net in 95 wt.% ethanol solution, performing ultrasonic treatment for 10min to remove surface impurities, and then washing with distilled water for 3-5 times to obtain a clean stainless steel net; the stainless steel net is rectangular, the length is 20cm, the width is 8cm, and the thickness is 0.3 mm;

mixing activated carbon and absolute ethyl alcohol, placing the mixture in an ultrasonic water bath for 10min, then dropwise adding 60% by mass of polytetrafluoroethylene emulsion, continuing to perform ultrasonic treatment for 10min, then placing the mixture in a water bath at 80 ℃ for stirring until the activated carbon and the absolute ethyl alcohol are completely separated and form a cluster, taking out the cluster of the activated carbon, softly softening the cluster of the activated carbon in an evaporation dish for 1min, and pressing the cluster of the activated carbon on a roller shaft of a roller press at 40 ℃ until the cluster of the activated carbon is flat to obtain an activated carbon cake; the dosage ratio of the activated carbon to the absolute ethyl alcohol is preferably 15 g: 120 mL; the dosage ratio of the activated carbon to the polytetrafluoroethylene emulsion is preferably 15 g: 1.67 mL; the thickness of the activated carbon cake is preferably 1.5 mm;

mixing conductive carbon black and absolute ethyl alcohol, placing the mixture in an ultrasonic water bath for 10min, then dropwise adding polytetrafluoroethylene emulsion with the mass fraction of 60%, continuing to perform ultrasonic treatment for 10min, then placing the mixture in a water bath at 80 ℃ for stirring until the conductive carbon black and the absolute ethyl alcohol are completely separated and form a cluster, taking out the cluster of the conductive carbon black, softly softening the cluster of the conductive carbon black in an evaporation dish for 1min, pressing the cluster of the conductive carbon black on a roller shaft of a roller press at 40 ℃ until the cluster of the conductive carbon black and the absolute ethyl alcohol is flat, then placing the cluster of the conductive carbon black in a muffle furnace at 340 ℃ for; the dosage ratio of the conductive carbon black to the absolute ethyl alcohol is preferably 10 g: 150 mL; the dosage ratio of the conductive carbon black to the polytetrafluoroethylene emulsion is preferably 10 g: 15.5 mL; the thickness of the conductive carbon black cake is preferably 1.5 mm;

hot-pressing the activated carbon cake onto the clean stainless steel net, and then hot-pressing the conductive carbon black cake onto the other surface of the clean stainless steel net to obtain an activated carbon air cathode sheet 3 with an activated carbon catalyst layer, a stainless steel net and a diffusion layer which are sequentially laminated; the temperature of the hot pressing is preferably 40 ℃; the thickness of the activated carbon air cathode sheet 3 is preferably 1-4 mm, and more preferably 2 mm. The invention adopts thicker active carbon air cathode sheets to better protect the electrodes and is suitable for long-time soil remediation work.

In the invention, the activated carbon air cathode sheet 3 is preferably wrapped by 1 layer on the outer surface of the porous PVC pipe 4; the active carbon air cathode plate 3 completely covers the outer surface of the porous PVC pipe 4; the active carbon air cathode plate 3 and the porous PVC pipe 4 are preferably bonded and sealed by glue.

The tubular active carbon air cathode provided by the invention comprises a cathode lead 5 arranged between the porous PVC tube 4 and the active carbon air cathode sheet 3, wherein the cathode lead 5 is inserted between the porous PVC tube 4 and the active carbon air cathode sheet 3. In the present invention, the cathode lead 5 is preferably a titanium sheet; one end of the cathode lead 5 is preferably flush with the bottom surface of the porous PVC pipe 4, and the other end is preferably higher than the top surface of the porous PVC pipe 4. In a specific embodiment of the invention, the thickness of the titanium sheet is preferably 0.1-2 mm, and more preferably 1 mm; the width of the titanium sheet is preferably 0.5-2 cm, and more preferably 1 cm.

In the invention, a schematic diagram of the tubular activated carbon air cathode is shown in an insert diagram at the lower left corner in fig. 1, wherein the upper edge and the lower edge of the tubular activated carbon air cathode are 1cm wide and are preferably wound and fixed by plastic packaging films.

The invention also provides a soil microorganism electrochemical restoration device, which comprises a box body, a box cover, the tubular active carbon air cathode and a carbon rod anode, wherein the tubular active carbon air cathode is arranged in the box body; the upper end of the box body is provided with an opening, an openable box cover is arranged above the box body, the box cover is provided with a first through hole, the bottom of the box body is provided with a second through hole opposite to the first through hole, and the tubular active carbon air cathode penetrates through the box cover and the box body through the first through hole and the second through hole; the carbon rod anode is arranged between the tubular active carbon air cathode and the side wall of the box body; the carbon rod anode comprises a carbon rod 1 and an anode lead 2 connected with the carbon rod 1; the box cover is provided with a first through hole and a second through hole, the first through hole is used for leading out an anode lead 2 of the carbon rod anode, and the second through hole is used for supplementing soil and moisture.

The soil microorganism electrochemical restoration device provided by the invention comprises a box body which is used as a container for electrochemical restoration. In the invention, the upper end of the box body is provided with an opening, the box body is preferably a cylindrical box body, and the material of the box body is preferably organic glass; the thickness of the side wall of the box body is preferably 1 cm; the bottom thickness is preferably 1 cm. As an embodiment of the present invention, the inner diameter of the case is 24cm, and the depth of the inside of the case is 8 cm.

The soil microorganism electrochemical remediation device provided by the invention comprises an openable box cover arranged above the box body and used for plugging an upper end opening of the box body. As an embodiment of the present invention, the box cover and the box body are connected by a flange, and the specific connection mode is as follows: the flange is arranged outside the upper edge of the box body, the flange is arranged on the edge of the box cover, and the flange of the box cover and the flange outside the upper edge of the box body are fixed through screws.

In the invention, the box cover is provided with a first through hole, the bottom of the box body is provided with a second through hole opposite to the first through hole, and the tubular active carbon air cathode penetrates through the box cover and the box body through the first through hole and the second through hole. In the present invention, the diameters of the first through hole and the second through hole preferably coincide with the outer diameter of the tubular activated carbon air cathode, and as an embodiment of the present invention, the diameters of the first through hole and the second through hole are preferably 5.5 cm; the outer diameter of the tubular activated carbon air cathode is preferably 5 cm.

In the invention, the height of the tubular activated carbon air cathode is preferably 15cm, and the tubular activated carbon air cathode preferably penetrates out of the bottom of the box body by 1-2 cm. In the invention, the contact position of the tubular active carbon air cathode and the bottom of the box body is preferably sealed by a plastic packaging film and glue. The tubular active carbon air cathode is limited to penetrate through the bottom of the box body, so that air can enter the box body conveniently, the soil remediation effect is improved, and the contact position of the tubular active carbon air cathode and the bottom of the box body is sealed, so that moisture seepage in the remediation process can be avoided.

In the invention, the box cover is provided with a first through hole and a second through hole, the first through hole and the second through hole are not in contact with the tubular activated carbon air cathode, the first through hole is used for leading out an anode lead 2 of a carbon rod anode, and the second through hole is used for supplementing soil and moisture. In the present invention, the diameters of the first through hole and the second through hole are independently preferably 0.5 to 1cm, and more preferably 1 cm. When the soil microbial electrochemical remediation device provided by the invention is used for soil remediation, the first through hole and the second through hole are preferably sealed, and the first through hole and the second through hole are preferably plugged by rubber plugs in the sealing mode.

The soil microorganism electrochemical remediation device provided by the invention comprises a carbon rod anode, wherein the carbon rod anode is arranged between the tubular activated carbon air cathode and the side wall of the box body, and is preferably arranged in the middle position between the tubular activated carbon air cathode and the side wall of the box body. In the present invention, the carbon rod anode includes a carbon rod 1 and an anode wire 2 connected to the carbon rod 1, and as an embodiment of the present invention, the carbon rod anode is formed by connecting four carbon rods 1 uniformly distributed around the tubular activated carbon air cathode, as shown in fig. 1. The invention adopts four carbon rods to form the carbon rod anode, which is beneficial to improving the degradation and electricity generation performance of the electrochemical repair device.

In the invention, the diameter of the carbon rod is preferably 0.5-2 cm, and more preferably 1 cm; the length of the carbon rod is preferably 3-10 cm, and more preferably 7.5 cm. In the invention, before the carbon rod is used, preferably, the carbon rod is washed for 3-5 times respectively by hydrochloric acid solution, sodium hydroxide solution and distilled water in sequence to remove surface impurities; the concentration of the hydrochloric acid is preferably 0.1mol/L, and the concentration of the sodium hydroxide solution is preferably 0.1 mol/L.

According to the invention, a titanium wire is preferably used as an anode lead 2 to be connected with the carbon rod 1 and led out from the first through hole; the diameter of the titanium wire is preferably 2 mm. In the present invention, it is preferable that the titanium wire is fixed at the first through hole by a rubber plug.

As an embodiment of the invention, the soil microorganism electrochemical remediation device further comprises an external resistor 6 for connecting the carbon rod anode and the tubular activated carbon air cathode to form a current loop. The invention preferably connects the anode lead 2 of the carbon rod anode and the cathode lead 5 of the tubular activated carbon air cathode through an external resistor 6.

mixing tested soil, carbon fiber and water to obtain slurry;

The invention mixes the tested soil, carbon fiber and water to obtain the slurry. In the present invention, the ratio of the amount of the soil to be tested, carbon fiber and water is preferably 3300 g: 1.65-13.2 g: 0.7-2L, more preferably 3300 g: 3.3 g: 1L of the compound. In the invention, the tested soil is preferably petroleum-polluted saline-alkali soil; the diameter of the carbon fiber is preferably 0.1-10 μm, and more preferably 5 μm; the length of the carbon fiber is preferably 0.5-3 cm, and more preferably 1 cm. In the present invention, the water is preferably distilled water. In the present invention, the mixing is preferably performed under stirring conditions, and the specific parameters of the stirring are not particularly limited in the present invention, and it is preferable that the soil to be tested, the carbon fibers and the water are uniformly mixed. According to the invention, the carbon fiber is doped into the soil, so that the conductivity of the soil is improved, on one hand, the degradation of petroleum pollutants by soil microorganisms can be promoted, and on the other hand, electric energy can be generated; meanwhile, the doped carbon fibers are easy to separate from the soil after the restoration is finished and can be repeatedly used.

After the slurry is obtained, the slurry is placed in a box body of the soil microorganism electrochemical restoration device, and water is added into the slurry through the second through hole for liquid sealing. In the invention, the slurry is preferably added between the tubular active carbon air cathode in the box body and the side wall of the box body in the technical scheme and is paved at the bottom of the box body, and the ratio of the thickness of the slurry to the height of the box body is preferably (3-7): 8, more preferably 6.5: 8. in the invention, the water adding amount of the water adding liquid seal is preferably 150-250 mL, more preferably 200mL, and the water adding liquid seal has the function of removing oxygen in soil so as to prevent consumption of electrons generated by degradation of petroleum pollutants and further inhibit generation of electric energy and promote mass transfer of pollutants and electrons in soil. According to the invention, after the water is added, the second through hole is preferably plugged by a rubber plug.

And after liquid sealing, connecting the anode lead 2 of the carbon rod anode and the cathode lead 5 of the tubular active carbon air cathode through an external resistor, and performing microbial electrochemical repair. In the present invention, the external resistance is preferably 100 to 1000 Ω, and more preferably 100 Ω.

In the microbial electrochemical remediation process, the microbes in the soil transfer electrons generated by degradation of petroleum pollutants to the anode through the carbon fibers, the electrons are transferred to the cathode through the external circuit, the electrons react with protons in the soil and oxygen in the air on the surface of the cathode to produce water, and the synchronous electrons flow through the external circuit to generate electric energy. And an external resistor is connected to form a closed circuit, an electric field is formed while current is formed, anions move to the anode under the action of the electric field, cations move to the cathode, and then salting out is carried out through an air cathode, so that soil desalination is realized.

In the repairing process, water is preferably added through the second through hole every 60 days to supplement soil moisture, and the mass ratio of the water adding amount to the soil is preferably 100-500 mL:3300g, and more preferably 200mL:3300 g.

The invention provides the application of the soil microorganism electrochemical remediation device or the method in the technical scheme in remediation of petroleum-polluted soil and synchronous power generation and desalination. The invention preferably connects the two ends of the external resistor 6 with a multi-channel voltage signal acquisition system 7, records the generated electric energy condition and synchronously uses the electric energy condition as a sensor to indirectly indicate the soil remediation condition.

The invention provides a novel method for efficiently recovering electric energy, removing petroleum hydrocarbon pollutants in soil, realizing soil desalination and synchronously recovering salt aiming at the ubiquitous problem of treating petroleum-polluted saline-alkali soil in China, and compared with the single purpose of removing pollutants achieved by physical, chemical and biological remediation reported at present, the novel method realizes the multifunctional effects of removing pollutants, generating electric energy and synchronously recovering salt during soil desalination, has stronger innovation and has the specific beneficial effects that:

firstly, the direct and efficient recovery of electric energy from soil is realized; the realized electrogenesis capability is the method with the longest electrogenesis time and the largest accumulated electrogenesis amount in the currently reported soil microorganism electrochemical system, and the generated electric energy can be used for the operation of a small sensor, such as a petroleum pipeline leakage alarm and the like;

secondly, the high-efficiency removal of petroleum hydrocarbon pollutants in the petroleum-polluted soil is realized, particularly the large-molecule, high-toxicity and difficult-to-degrade aromatic hydrocarbon pollutants; by providing the solid anode electron receiver, the enrichment of indigenous electrogenic microorganisms in the soil is induced, so that bioelectric current is generated to stimulate the activity of petroleum hydrocarbon degrading microorganisms in the soil, and finally the removal rate of the petroleum hydrocarbon and components thereof is improved, particularly aromatic hydrocarbon pollutants in the soil are obviously removed, so that the biotoxicity of the soil is obviously reduced, and the improvement of the activity of the degrading microorganisms is facilitated in turn;

thirdly, the removal and recovery of salt in the soil are realized simultaneously; in the constructed soil microbial electrochemical system, a biological electric field is formed while soil bioelectric current is formed, under the combined action of the biological electric field and water evaporation, salt-based ions in soil are transported to the surface of an active carbon air cathode, pass through the cathode and encounter air to be salted out and recycled to a tubular air cathode, and the salt in the soil is directly recycled; the value of the recovered salt reduces the repair cost, and the removal of the salt can obviously reduce the osmotic pressure of the soil, thereby relieving the inhibiting effect of high salinity on the microbial activity of the soil;

fourthly, the investment and maintenance cost is low; according to the invention, in the repairing process, biological and chemical exogenous substances such as a microbial inoculum, a carbon source, a nitrogen source, a buffer solution and the like are not required to be added, and voltage is not required to be applied, so that the aims of soil repairing and desalting can be fulfilled, high-efficiency electricity generation is synchronously realized, and the repairing cost can be reduced by the generated electric energy; the adopted electrode is a carbon-based electrode, and the doped carbon fiber is easy to separate from the repaired soil and can be recycled, so that the repair cost is reduced; compared with the prior report that the cathode catalyst uses noble metal platinum, the material cost of the repairing device is greatly reduced by using the activated carbon catalyst layer; meanwhile, in the whole repairing process, only the soil moisture content needs to be maintained, so that the maintenance cost is low;

fifthly, the environment is friendly, and the safety is high; the invention can recover electric energy from the petroleum hydrocarbon degradation process only by depending on soil indigenous microorganisms, and simultaneously drives the salt in the soil to move directionally by depending on the in-situ generated bioelectric current, so as to realize triple effects of pollutant degradation, energy recovery and soil desalination under the condition of basically no interference to the original habitat of the soil; electrons generated by the degradation of petroleum hydrocarbon pollutants finally react with oxygen in the air to generate water, so that the method has no secondary pollution and is an environment-friendly novel ecological restoration technology; meanwhile, the repairing device operates at normal temperature and normal pressure, the reaction is mild, no harmful gas is generated, no foreign bacteria invasion risk exists, and the implementation safety is high;

sixth, the invention has simple structure, convenient operation and easy popularization and implementation; compared with the previous reports, the tubular active carbon air cathode adopted by the invention can be directly inserted into the polluted soil, and can simultaneously play a role of enhancing degradation in cooperation with the anode, thereby improving the efficiency of the constructed device. The device can be used for in-situ repair besides ex-situ repair, so that the popularization and implementation are strong;

seventh, the invention can be used for removing organic pollutants such as antibiotics and pesticides, and has strong universality; the constructed soil microbial electrochemical system performs the function of enhancing degradation based on the microbial community which is abundant in soil, so that the invention is theoretically suitable for all biodegradable organic pollutants, for example, the degradation of tetracycline and metolachlor can be obviously promoted, and the invention can also be suitable for other organic polluted soil such as antibiotics, pesticides, hormones and the like besides the petroleum polluted soil.

The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1

The tubular activated carbon air cathode provided in this example is shown in the lower left-hand insert in fig. 1.

(1) Manufacturing the activated carbon air cathode sheet 3:

shearing a stainless steel net with the width of 8cm and the length of 20cm, carrying out ultrasonic treatment in 95 wt.% ethanol solution for 10min to remove surface impurities, and then washing with distilled water for 3-5 times to obtain a clean stainless steel net;

putting 15g of activated carbon into a beaker, adding 120mL of absolute ethyl alcohol, carrying out ultrasonic treatment in an ultrasonic water bath for 10min, slowly dropwise adding 1.67mL of polytetrafluoroethylene emulsion with the mass fraction of 60% by using a liquid-moving gun, carrying out ultrasonic treatment for 10min, putting the mixture into a water bath at 80 ℃, simultaneously stirring until the activated carbon and the absolute ethyl alcohol are completely separated and form a cluster (about 1h), taking out the activated carbon cluster, softly putting the activated carbon cluster in an evaporation dish for 1min, and pressing the cluster on a roller shaft of a roller press at 40 ℃ until the cluster is flat to obtain an activated carbon cake with the thickness of 1.5 mm;

hot-pressing the activated carbon cake onto a stainless steel net at 40 ℃, wherein the thickness of the activated carbon catalyst layer after hot pressing is 1 mm;

putting 10g of conductive carbon black in a beaker, adding 150mL of absolute ethyl alcohol, carrying out ultrasonic treatment in an ultrasonic water bath for 10min, slowly dropwise adding 15.5mL of polytetrafluoroethylene emulsion with the mass fraction of 60% by using a liquid-moving gun, continuing the ultrasonic treatment for 10min, then putting the mixture in a water bath at 80 ℃, simultaneously stirring until the conductive carbon black and the absolute ethyl alcohol are completely separated and form a cluster (about 40min), taking out the cluster of the conductive carbon black, softly softening the cluster of the conductive carbon black in an evaporation dish for 1min, pressing the cluster of the conductive carbon black to be flat on a roller shaft of a roller press at 40 ℃, then calcining the cluster of the conductive carbon black in a muffle furnace at 340 ℃ for 20min, taking out and cooling to obtain a conductive carbon black cake with the; and (3) hot-pressing the conductive carbon black cake to the other surface of the stainless steel net at 40 ℃ to form a diffusion layer, thus preparing the activated carbon air cathode sheet 3 with the thickness of 2 mm.

(2) Production of porous PVC pipe 4

And (3) taking a PVC pipe with the diameter of 5cm and the length of 15cm, and electrically drilling holes with the diameter of 0.5cm and the hole interval of 1cm to obtain the porous PVC pipe 4.

(3) Assembly of tubular active carbon air cathode

Wrapping the active carbon air cathode sheet 3 on the outer surface of the porous PVC pipe 4, wherein the wrapping layer is one layer, and the diffusion layer is in contact with the porous PVC pipe 4 and is bonded and sealed by glue; and a titanium sheet 5 is clamped between the diffusion layer and the tube to be used as a cathode lead, the thickness of the titanium sheet 5 is 1mm, the width of the titanium sheet is 1cm, and the upper edge and the lower edge of the tubular active carbon air cathode are wound and fixed by plastic packaging films in a width of 1 cm.

Example 2

The soil microorganism electrochemical remediation device provided by the embodiment is shown in fig. 1.

The repairing device comprises a cylindrical box body with the inner diameter of 24cm and the depth of 8cm, and the upper edge of the box body is provided with a flange; a through hole with the diameter of 5cm is formed in the center of the bottom of the box body, and a through hole with the diameter of 5cm is also formed in the center of the box cover with the flange and is opposite to the hole in the center of the bottom of the box body; in addition, two holes with the diameter of 1cm are reserved on the box cover and are respectively a first through hole and a second through hole, the first through hole is used for leading out an anode lead of the carbon rod current collector, and the second through hole is used for supplementing soil moisture in the later period; one end of the tubular active carbon air cathode prepared in the embodiment 1 penetrates through a through hole in the center of the bottom of the box body by 1-2 cm, and the contact position is sealed by a plastic packaging film and glue;

3300g of the saline-alkali soil polluted by the tested petroleum and 3.3g of carbon fiber with the diameter of 5 μm and the length of 1cm are weighed, 1L of distilled water is added, the mixture is filled into the box body after being fully stirred uniformly, the soil depth is 6.5cm, and the cathode area which actually plays a role is deduced to be 102cm²(ii) a Taking four carbon rods with the length of 7.5cm and the diameter of 1cm, washing the four carbon rods with 0.1mol/L hydrochloric acid, 0.1mol/L sodium hydroxide solution and distilled water for 3-5 times respectively before use to remove surface impurities, then uniformly inserting the carbon rods into the middle positions of the air cathode of the tubular activated carbon and the side wall of the box body at equal intervals (as shown in figure 1), connecting the four carbon rods 1 with titanium wires 2 with the diameter of 2mm, and finally leading out from the first through hole to obtain an anode lead; penetrating a through hole in the center of the box cover through the other end of the tubular active carbon air cathode, and fixing a box cover flange and an upper edge outer flange of the box body by using screws to finish the assembly of the soil microbial electrochemical remediation device;

adding 200mL of distilled water into the saline-alkali soil polluted by the tested petroleum through the second through hole, and plugging the small hole by using a rubber plug; simultaneously, plugging the first through hole by using a rubber plug, namely fixing the titanium wire; connecting a titanium sheet 5 and a titanium wire 2 of the repairing device with an external resistor 6, connecting two ends of the external resistor 6 with a multi-channel voltage signal acquisition card (PISO U813)7 and an electrochemical workstation, setting the external resistor to be 100 omega, starting repairing, and adding 200mL of distilled water through the second through hole every 60 days to supplement soil moisture in the repairing process.

Comparative example 1

A blank control group was set: 350g of petroleum-polluted saline-alkali soil is weighed, 105mL of distilled water is added, the mixture is uniformly stirred and mixed, then the mixture is loaded into a rectangular box body with the length of 6cm, the width of 6cm and the height of 9cm, the depth of the loaded soil is 6.5cm, 20mL of water is added for sealing, and then the box body is covered to be used as a control group CK for treatment.

Comparative example 2

Untreated virgin petroleum-contaminated saline-alkali soil was taken as a control group OS.

Test example 1

The production efficiency of the soil microorganism electrochemical restoration device is as follows:

the output voltage of the repairing device provided by the embodiment 2 is collected by a multi-channel voltage signal collecting card, a voltage value is collected every 1min, and an average value of the output voltage is obtained every 30min and is recorded at the same time; the accumulated output electric quantity adopts a formula

Calculating, wherein U is the collected output voltage value, R is the external resistor, the resistance value is 100 omega, T is the operation time of the repairing device for 759 days, and the integral of time T in the formula takes 1800s as a time unit gradient; the output current density of the repairing device is calculated as I ═ U/(R.A), wherein A is the action area 102cm of the actual tubular active carbon air cathode²；

The output voltage of the repairing device is shown in fig. 2, and in general, during the period of 759 days of continuous electric energy generation of the repairing device, the output voltage shows two peaks; the first peak appears between 4.5 and 5.5 days, and the average value is 206 +/-4 mV (the average value of 24h is converted into the current density and is normalized to the area of the cathode is 202 +/-4 mA · m^-2Normalizing the power density to 41.77 +/-0.02 mW.m^-2) During the period, at 120h, the maximum value of 213mV (209mA · m) is reached^-2，44.48mW·m^-2) (ii) a The second time of peak emergence is from day 41, and extends to day 257, the output voltage of the system is always above 200 mV, and the average value is 230 + -6 mV (average value of 216 days, 226 + -5 mA · m^-2，52.03±0.03 mW·m^-2) During this period, at 2121h, the maximum value of 405mV (397mA · m)^-2，160.81 mW·m^-2) (ii) a Then, from 258 days to 466 days, although the output voltage of the prosthetic device gradually decreased, the output voltage was still over 100mV, with a mean value of 150. + -.50 mV (mean value of 208 days, 147. + -. 49 mA · m)^-2，21.91±2.40mW·m^-2) (ii) a Then, from 467 th day to 759 th day after the repair is finished, the output voltage of the repair device gradually decreases from 100mV to 58 mV;

the cumulative generated charge of the prosthetic device is shown in fig. 3; during 759 days, the system generates 85418C (coulomb) in total, calculated at 3.6C ═ 1mAh (milliamp-hour), 23727mAh in total, and generates 113C, i.e. 31mAh, on average per day. At present, the battery capacity of a Mate 30 mobile phone is 4200 mAh, the battery capacity of an iPhone 11 mobile phone is 3110mAh, and the battery capacity of a built-in battery of a common wireless transmitter such as humidity, temperature, pressure and the like is 2000-7000 mAh, so that the electric quantity generated by the repairing device can be absolutely supplied to a small sensor device, and the generated electric energy has a utilizable value.

Test example 2

The soil microorganism electrochemical restoration device has the following effects of removing petroleum hydrocarbon and components thereof in soil:

after the soil samples repaired in the example 2 and the comparative example 1 are frozen and dried for 48 hours at the temperature of minus 60 ℃ and under the pressure of 20Pa, the soil samples are ground and sieved by a 100-mesh sieve after being confirmed to be completely dried, and the contents of petroleum hydrocarbon and components (alkane, aromatic hydrocarbon, polar substances and asphaltene) thereof are measured by a gravimetric method: weighing 2g of ground soil sample, using dichloromethane as an extracting agent, and continuously extracting for 3 times by using 20mL of the extracting agent each time through multi-step ultrasonic extraction, wherein the extraction time is 30min each time; mixing the extraction liquid obtained by the third extraction, steaming the extraction agent dichloromethane at 42 ℃, quantifying the total petroleum hydrocarbon content through mass difference, and then converting the total petroleum hydrocarbon content to unit soil mass;

the alkane and arene content is measured by adopting a glass packed column leaching separation method: the filler is pretreated silica gel, pretreated neutral alumina and treated anhydrous sodium sulfate; pretreatment of anhydrous sodium sulfate: wrapping anhydrous sodium sulfate with tinfoil, calcining at 400 deg.C in a muffle furnace for 6h, cooling to room temperature in the muffle furnace, and sealing with n-hexane; pretreatment of silica gel: ultrasonically cleaning silica gel for 30min by using a mixed solution of dichloromethane and n-hexane (volume is 1:1), removing filtrate, spreading the mixture on a piece of tinfoil, drying the tinfoil in a fume hood, baking the tinfoil in an oven at 130 ℃ for 16h, cooling the tinfoil, dropwise adding 2% of distilled water gradually, shaking the tinfoil uniformly, transferring the tinfoil into a ground bottle, and sealing the tinfoil with n-hexane liquid; the pretreatment method of the neutral alumina is the same as that of silica gel; adding 12cm, 6cm and 1cm of pre-prepared silica gel, neutral alumina and anhydrous sodium sulfate into a glass column (with an inner diameter of 1cm and a length of 25cm) from bottom to top in sequence, and cutting to record that normal hexane liquid seal is needed when each filler is filled, and each filler needs to be tamped;

leaching out alkane: sucking out the excessive n-hexane on the upper layer of the column, and keeping the n-hexane to be higher than an anhydrous sodium sulfate interface by about 1 cm; adding two Pasteur suction pipes of n-hexane (about 3mL) into a triangular flask which is weighed and used for measuring the total petroleum hydrocarbon, and carrying out ultrasonic treatment to completely dissolve the n-hexane; then adding a small amount of the filtrate into a pre-filled column one by one, opening a valve at the lower end of the column, leaching residues in the column for a small amount of times by using 20mL of n-hexane, and collecting a leaching solution; after the leaching solution is distilled at 42 ℃ to remove the solvent n-hexane, quantifying the alkane content, and then converting the alkane content to the unit soil mass;

leaching aromatic hydrocarbon: stopping leaching of alkane when the liquid level is about 1cm above anhydrous sodium sulfate, continuously leaching the column by using 70mL of mixed solution of normal hexane and dichloromethane (the volume ratio is 1:1) for a small amount of times, collecting leaching liquid, evaporating the solvents of normal hexane and dichloromethane at 42 ℃, quantifying the content of aromatic hydrocarbon, and then converting the content of aromatic hydrocarbon to the unit soil mass;

the polar and asphaltene content is obtained by subtracting the alkane and aromatic content from the total petroleum hydrocarbon content.

In order to more fully analyze the degradation performance of the soil microbial electrochemical system, six typical locations were selected for soil samples, each taken from the surface to the bottom, labeled S1, S2, S3, S4, S5 and S6, as shown in fig. 4, where S1 is the region between the cathode and the anode near the cathode, S2 is the region between the anode and the side wall of the tank near the anode, and S3 is the region between the anode and the side wall of the tank near the side wall of the tank; s4 is the cathode vicinity, S5 is the two anode middle regions, S6 is the box side wall vicinity; marking the original soil sample before restoration as OS, and marking the soil sample of the control treatment group as CK;

the removal of total petroleum hydrocarbons in the soil after the electrochemical remediation by the soil microorganisms is shown in FIG. 5. from FIG. 5, it can be seen that the content of total petroleum hydrocarbons in the control treatment group CK is reduced by 7 after the remediation time is over681±464mg·kg^-1(ii) a The total petroleum hydrocarbon removal in all soil samples except soil sample S6 was higher than CK; wherein the removal amount of total petroleum hydrocarbon in the soil sample S2 (namely the soil near the carbon rod current collector) is the maximum, and is 21725 +/-2528 mg-kg^-1183% higher than CK; next, soil sample S1 (i.e., soil near the tubular activated carbon air cathode) was obtained, from which total petroleum hydrocarbons were removed in an amount of 13677. + -. 793 mg-kg^-178% higher than CK; again soil sample S3, the total petroleum hydrocarbon removal was 11571 + -851 mg-kg^-1Is 51% higher than CK; statistical analysis showed that the total petroleum hydrocarbon removal in the S1, S2, and S3 soil samples was significantly higher than CK (p < 0.05), and in the soil samples S4 and S5, the total petroleum hydrocarbon removal was 27% and 7% higher than CK, respectively.

The removal of alkanes from the soil after the electrochemical remediation by soil microorganisms is shown in FIG. 6; as can be seen from FIG. 6, after the completion of the repairing period, the amount of alkane removed from the CK-treated control group was 3514. + -. 838 mg/kg^-1Unlike the removal of the total petroleum hydrocarbon content in the soil sample, the removal of the alkane in the soil sample S1 (i.e., the soil near the tubular activated carbon air cathode) was the highest, namely 5178 + -596 mg-kg^-1The CK was 47% higher than that in the control group and statistically significant (p < 0.05). For soil sample S2 (i.e., soil near the carbon rod current collector), the alkane removal amount was 4576. + -. 395 mg-kg^-1Is 30% higher than CK; in another soil sample S4 adjacent to the tubular activated carbon air cathode, the alkane removal amount was 3904. + -. 679 mg-kg^-111% higher than CK; in soil samples S3 and S5, the amount of alkane removed was similar to CK.

The removal of aromatic hydrocarbons from soil after electrochemical remediation by soil microorganisms is shown in fig. 7; as can be seen from FIG. 7, after the completion of the repair time, the amount of aromatics removed from the control-treated CK was 2484. + -. 309 mg/kg^-1Similar to the removal of total petroleum hydrocarbons from soil, the removal of aromatic hydrocarbons from soil sample S2 (i.e., soil near the carbon rod current collector) was the highest, reaching 13844 + -2119 mg-kg^-1Compared with the CK of the control treatment group, the CK is increased by 457 percent; in soil samples S1 and S3, the amount of aromatics removed was 6551. + -. 1064 mg-kg, respectively^-1And 5233. + -.788mg·kg^-1Increased by 164% and 111%, respectively, compared to CK, and statistically significant levels (p < 0.05); in soil samples S4 and S6, the removal amount of aromatics was 33% and 38% higher than CK, respectively.

The removal of polar substances and asphaltenes in soil after electrochemical remediation by soil microorganisms is shown in FIG. 8; as can be seen from FIG. 8, the amount of polar substances and asphaltenes removed in the control CK was 1683. + -. 188 mg/kg^-1(ii) a In soil samples S2 and S3, the removal amounts of polar substances and asphaltenes were high, and were 3304. + -. 191 mg/kg^-1And 3218 + -288 mg.kg^-1Compared with CK, the increase is 96% and 91% respectively; next are soil samples S4 and S5, which showed 48% and 50% increase in polar and asphaltene removal, respectively, compared to CK, and which achieved statistically significant levels (p < 0.05). In soil sample S1, the removal amount of polar substances and asphaltenes was 16% higher than CK.

In conclusion, the constructed soil microbial electrochemical remediation device has good removal efficiency on petroleum hydrocarbon and components thereof in soil, hydrocarbon pollutants in the petroleum-polluted soil are obviously removed after the soil microbial electrochemical remediation device is constructed for remediation, particularly in the soil near a cathode and an anode, the petroleum hydrocarbon pollutants in the soil, especially aromatic hydrocarbon substances which have high toxicity and are difficult to biodegrade, are greatly removed, and the biotoxicity of the petroleum-polluted soil and the ecological risk to the surrounding environment such as underground water are obviously reduced.

Test example 3

The soil microorganism electrochemical restoration device has the following effects of removing salt in soil:

the salinity content in the soil is an index directly reflecting the salinity and alkalinity of the soil: weighing 2g of the soil samples of example 2 and comparative examples 1-2 into a centrifuge tube, adding 10mL of deionized water, performing vortex oscillation for 30min, and performing 5000 r.min^-1Centrifuging for 5min under the condition, taking 6mL of supernatant fluid in an evaporation dish with the weighed weight, putting the supernatant fluid in an oven to evaporate to dryness, and cooling the supernatant fluid in a drying dish; adding a small amount of 150 g.L into the evaporated evaporation pan^-1Hydrogen peroxide and thenEvaporating and cooling for at least 3 times until the solid in the evaporating dish is white; and finally, cooling the evaporating dish with the white solid, weighing, recording the weight, putting the evaporating dish into the oven again for evaporation for 1 hour, recording the weight after cooling, repeating the step until the weight difference between the two times is less than 0.001g, and quantifying the salt content in the soil.

The conductivity of the soil is also an important index for reflecting the content of salt in the soil: weighing 2g of the soil samples of example 2 and comparative example 1 into a 50mL centrifuge tube, adding 10mL of deionized water, performing vortex oscillation for 30min, and performing 5000 r.min^-1Centrifuging for 5min under the condition, and measuring the conductivity value of the soil supernatant by using a Merterla soil conductivity measuring instrument.

The content of salt in the soil after the electrochemical remediation of the soil microorganisms is shown in fig. 9, and the change of the soil conductivity after the electrochemical remediation of the soil microorganisms is shown in fig. 10; as can be seen from FIGS. 9 to 10, the total amount of water-soluble salts in the original soil sample OS reached 31.5. + -. 0.4 g/kg^-1(3.15%) and a conductivity of 8.11. + -. 0.07mS cm^-1The salinization of the tested petroleum-polluted soil is serious; after the restoration time is over, the salt content and the soil conductivity in the CK are respectively reduced to 18.9 +/-5.2 g-kg^-1And 5.39. + -. 1.18 mS. cm^-1A 40% and 34% reduction, respectively, compared to OS and statistically significant levels (p < 0.05); after the soil microbial electrochemical treatment, the salt content and the soil conductivity of the soil samples from S1 to S6 are both obviously lower than that of an original soil sample OS and that of a control group CK, and the two indexes in the soil samples from the six soil samples are not significantly different statistically (p is less than 0.05); compared with OS, the salt content and the soil conductivity of the six soil samples are respectively reduced by 61-66% and 69-74% (p is less than 0.05); compared with CK, the salt content and the soil conductivity of six soil samples are respectively reduced by 35-43% and 53-62% (p is less than 0.05); therefore, in the tested petroleum-polluted saline-alkali soil, the constructed soil microbial electrochemical system can obviously remove the salt in the soil, and a better soil desalting effect is shown. The removal of salt in the soil can obviously reduce the osmotic pressure of the soil and relieve the adverse stress of growth of microorganisms and the like in the soil; and, in repairingAt the end, relatively purified soil salt is recovered from the tubular activated carbon air cathode of the soil microbial electrochemical system (as shown in fig. 11), which indicates that the remediation device can directly recover salt from saline-alkali soil, and opens up a new way for development and utilization of salt in soil.

Test example 4

The soil quality improvement efficiency after the soil microbial electrochemical remediation assembly and restoration is as follows:

the pH value of soil is an important characteristic parameter of soil property and even soil quality, and partial acid or partial alkali can reduce the soil quality: weighing 2g of the soil samples of example 2 and comparative examples 1-2 into a 50mL centrifuge tube, adding 10mL of deionized water, performing vortex oscillation for 30min, and performing vortex oscillation at 5000 r.min^-1Centrifuging for 5min under the condition, and measuring the pH value of the soil supernatant by using a Mertelle soil pH meter.

The change of the soil pH after the electrochemical remediation of soil microorganisms is shown in FIG. 12, and the change of the soil quality can be reflected from the side through the change of the soil pH; as can be seen from FIG. 12, after the remediation is finished, the pH of the soil in CK is increased from 7.95 +/-0.01 of the original soil to 8.12 +/-0.14; the pH of the soil samples from the S1 to the S6 is 7.40-7.57 (the difference between the soil samples is not obvious), the pH is statistically and obviously lower than CK and OS (p is less than 0.05), the pH of the soil repaired by the soil microbial electrochemical system generally tends to be neutral, and the quality of the soil repaired by the constructed system is improved.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Claims

1. A soil microorganism electrochemical restoration device is characterized by comprising a box body, a box cover, a tubular active carbon air cathode and a carbon rod anode arranged in the box body;

the tubular active carbon air cathode comprises a porous PVC pipe (4) and an active carbon air cathode sheet (3) wrapped on the outer surface of the porous PVC pipe (4); a cathode lead (5) is inserted between the porous PVC pipe (4) and the active carbon air cathode sheet (3), and the cathode lead (5) is exposed;

the active carbon air cathode sheet (3) comprises an active carbon catalysis layer, a stainless steel net and a diffusion layer which are sequentially laminated; the diffusion layer is in contact with the porous PVC pipe (4);

the carbon rod anode is arranged between the tubular active carbon air cathode and the side wall of the box body; the carbon rod anode comprises a carbon rod (1) and an anode lead (2) connected with the carbon rod (1); the four carbon rods (1) are uniformly distributed on the periphery of the tubular active carbon air cathode; the four carbon rods are connected through an anode lead (2);

the box cover is provided with a first through hole and a second through hole, the first through hole is used for leading out an anode lead (2) of the carbon rod anode, and the second through hole is used for supplementing soil moisture.

2. The soil microorganism electrochemical restoration device according to claim 1, wherein the diameter of the holes on the porous PVC pipe (4) is 0.1-1 cm, and the distance between the holes is 0.5-2 cm.

3. The soil microorganism electrochemical remediation device of claim 1, wherein the activated carbon air cathode sheet (3) is 1-4 mm thick.

4. The soil microbial electrochemical remediation device of claim 1, wherein said cathode lead (5) is a titanium sheet; one end of the cathode lead (5) is flush with the bottom surface of the porous PVC pipe (4), and the other end of the cathode lead is higher than the top surface of the porous PVC pipe (4).

5. The soil microbial electrochemical remediation device of claim 1 wherein said cover is flanged to said housing.

6. A method for electrochemically remediating soil microorganisms is characterized by comprising the following steps:

mixing tested soil, carbon fiber and water to obtain slurry;

placing the slurry in a box body of the soil microbial electrochemical remediation device as claimed in any one of claims 1 to 5, and adding water into the slurry from the second through hole for liquid sealing;

and connecting the anode lead (2) of the carbon rod anode with the cathode lead (5) of the tubular activated carbon air cathode through an external resistor to carry out microbial electrochemical repair.

7. The method according to claim 6, wherein the slurry is prepared by using the soil, the carbon fiber and the water in a ratio of 3300 g: 1.65-13.2 g: 0.7-2L.

8. Use of the soil microbial electrochemical remediation device of any one of claims 1 to 5 or the method of any one of claims 6 to 7 for the simultaneous generation and desalination of remediated petroleum contaminated soil.